AS usual, the annual display of watercolours and drawings by Joseph Mallord Turner is being shown at the National Gallery of Ireland this month. Of the 35 works on display, 31 were bequeathed to the gallery by Henry Vaughan in 1900, with the proviso that they must be exhibited only at this time of year when the light is lowest. The watercolours feature views of Switzerland and Venice, English coastal towns, seascapes, Welsh castles and German fortresses. As the show indicates, this medium inspired the artist throughout his long and prolific life. For the first time at the National Gallery, watercolours by three painters who had an influence on the young Turner will be shown. The three are John Robert Cozens, Edward Dayes and Paul Sandby, each of whom is represented by one work. At the same time, a new publication, Turner at the National Gallery of Ireland, has just been published, price £9.95. The author of this colour-illustrated catalogue is Barbara Dawson of the Hugh Lane Municipal Gallery of Modern Art. Seven lectures exploring different aspects of Turner and his art are being given at the National Gallery. Tomorrow at 3 p.m. Adrian Le Harival speaks of "New Light on Turner". Admission to both the exhibition and the lectures is free.